nektos
Increase parallel job limit
Act version
act version 0.2.76
Feature description
I would like to request an enhancement to allow act to run jobs in greater parallelism by default. I primarily contribute by submitting pull requests to various GitHub repositories maintained by others. Since GitHub Actions require maintainer approval before running CI, I frequently use act for local testing. When utilizing matrix jobs to test across multiple environments, the hard limit of 4 concurrent jobs causes slower execution times.
I understand that this limit was intentionally introduced (see fix: add simple concurrency limit by catthehacker · Pull Request #823 · nektos/act). Although it is possible to control the concurrency via file configuration, I often work on many OSS projects and make temporary patches without the intention of adding or committing non-standard configuration files. Having to modify files every time not only feels cumbersome, but there is also a risk of accidentally committing these settings.
I propose that when sufficient CPU and memory resources are available, act should automatically allow a higher number of parallel jobs without requiring manual file-based configuration changes. This improvement would greatly streamline local testing workflows by significantly reducing the total test execution time when running multiple jobs concurrently.
While the source code suggests that excessive parallelism isn't necessary, I've encountered practical limitations with the current settings.
When working with repositories that have extensive matrix patterns like awakesecurity/proto3-suite: Haskell Protobuf Implementation, I found that the default 4-way parallelism significantly underutilizes my Ryzen 9950X3D's resources. This results in slower local execution times than what my hardware is capable of.
